1. Technical Field
This invention relates to a process for removing organics, particulates and dissolved metal contaminates from waste fluids by electrolysis, more particularity, the invention utilizes a high pressure electrocoagulative process to convert the dissolved metal contaminates to suspended particles, utilizing dissolved gases where upon release of the pressure, the dissolved gases and suspended particles rise to the waste fluid surface to facilitate removal of the metal contaminates and an organics removal means is used to remove the organic contaminates.
2. Description of the Technology and Art
Electrocoagulation is a process by which electrolysis is combined with precipitation and flocculation to remove contaminates from wastewater. In this process, an electric current is used to neutralize, reduce and/or oxidize ionic, particulate or other dissolved species and contaminates, thereby allowing such contaminants to be precipitated and removed from stable suspensions and emulsions, such as in wastewater fluids. The electric current (voltage) provides the electromotive force required to drive the chemical reactions. The reactor utilized in the process contains a series of substantially parallel electrolytic plates or electrodes through which the wastewater to be treated travels in a serpentine path while being exposed to a strong electric field or voltage.
The electromotive force present in the reactor overcomes the Stem""s forces disrupting the outer electron orbitals of dissolved ionic species and neutralizes colloidal particulate charges resulting in the destabilization of contaminants. The principal cathodic reaction is the reduction of hydrogen ion to hydrogen gas and the reduction of the valence state of some dissolved species. The anode sacrifices metallic ions into solution in accordance with Faraday""s Law and liberates oxygen gas. The newly formed compounds may be precipitated as acid resistant metallic oxide complexes that may be agglomerated or flocculated and removed by conventional liquid-solids separation methodologies.
However, it has been difficult to remove contaminates by electrocoagulation that do not readily form a precipitant. It is possible to convert such contaminates to gaseous compounds, such as chlorine gas from chloride and ammonia gas from nitrate. Also, some organic compounds may be oxidized or reduced to gaseous species. Electrolysis of water molecules in the waste fluid liberates oxygen and hydrogen gas by simultaneous oxidation and reduction reactions. At atmospheric pressure, these gases evolve as bubbles that must be removed prior to separation of the precipitate.
A prior art electrocoagulation method is the Kaselco system, described in U.S. Pat. No. 5,928,493. This method utilizes an electrocoagulation reactor to precipitate contaminants. After the wastewater fluid is treated in an electrolytic reactor, the fluid enters an agitated de-foam tank where the entrained gas bubbles are allowed to dissipate and escape. A flocculating agent is added and the water then enters a clarifier where particulates are separated by conventional sedimentation technology. The Kaselco system, however, is not capable of removing entrained gas bubbles and clarifying flocs from the wastewater in a single step and includes additional tankage, mixers and piping.
However, there is a need for a pressurized electrocoagulation process in which the oxygen and hydrogen gases produced will remain in solution. These dissolved gases also remain available for subsequent oxidation-reduction reactions with wastewater contaminates. When the pressure is released, the dissolved gases evolve from solution as microfine bubbles to encourage rapid flotation and separation of agglomerated particulates to a liquid surface.
The present invention meets these needs and other needs.
In accordance with the present invention, an electrocoagulation process for removing organics, particulates and metal contaminants from a waste fluid to form a clarified waste fluid has been discovered which includes the steps of supplying the waste fluid to a reactor vessel which have a plurality of substantially parallel electrolytic plates. The electrolytic plates have a positive or a negative charge that is provided by a power supply. The waste fluid is pressurized to pressure from about 1 to about 100 psig and then reacted with the charged electrolytic plates. Water, organics, particulates and metal contaminants form dissolved gases and form precipitate particles in the pressurized waste fluid. The pressure of said waste fluid is reduced to release the dissolved gases and to cause said precipitate particles to rise in said vessel. Precipitate particles are removed from the vessel to form the clarified waste fluid.
The invention also includes an apparatus for treating organics, particulates and metal contaminates in a waste fluid using electrocoagulation which comprises a collection means having an inlet for collecting said waste fluid. A reactor vessel is in fluid communication with said collection means, said reactor vessel having a vessel pressure and a plurality of substantially parallel positively and negatively charged electrolytic plates. A power supply connected to said electrolytic plates, said power supply provides a voltage that causes said contaminants to react with water and said electrolytic plates to form dissolved gases and precipitate particles in said waste fluid. A pressurizing means in fluid communication with said reactor vessel for pressurizing said waste fluid to said vessel pressure of said reactor vessel. A flotation chamber in fluid communication with said reactor vessel, said flotation chamber having a chamber pressure below said vessel pressure so that dissolved gases evolve from said waste fluid causing said precipitate particles to float to a fluid surface for removal to form a clarified waste fluid.
The apparatus of this invention may also include means for removal of organics from the clarified waste fluid to form a purified fluid stream. The organics removal means includes a reactor having a membrane and/or bioreactor.